Kitten Giardia and Coccidia: Parasites That Cause Stubborn Diarrhea

By Tailwisp Editorial TeamUpdated October 20, 20264 min read

When a kitten has diarrhea that comes and goes despite deworming, a different kind of parasite may be to blame. Giardia and coccidia are protozoa, single-celled organisms that live in the gut. They are common in kittens, especially from shelters, and often cause trouble that standard dewormers do not touch.

Giardia

Giardia is picked up by swallowing cysts in contaminated water, food or feces, or by grooming. It attaches to the lining of the small intestine and interferes with absorption. Signs include:

• Soft, pale, greasy, foul-smelling stool, sometimes with mucus.
• Intermittent or chronic diarrhea.
• Weight loss or poor growth.
• Vomiting in some.
• Some kittens show no signs.

Coccidia

Coccidia (often Cystoisospora) are spread by oocysts shed in feces, which become infective after a day or two in the environment. Kittens can be infected by the mother, or by contaminated surroundings. Signs include:

• Watery or mucus-filled diarrhea, sometimes bloody.
• Dehydration.
• Poor appetite.
• Weight loss and failure to thrive.
• Severe illness in very young or stressed kittens.

Many adult cats carry coccidia without signs, and shed oocysts, infecting kittens.

Diagnosis

• Fecal flotation shows coccidia oocysts and giardia cysts, though cysts shed intermittently, so repeat testing may be needed.
• Fecal antigen tests or PCR are more sensitive for giardia.
• A fresh sample is important, within a few hours or refrigerated.

Bring samples from several days if possible. See kitten diarrhea for how to collect.

Treatment

• Giardia: typically fenbendazole or metronidazole, as your vet prescribes, sometimes combined, for several days. Bathing the kitten to remove cysts from the coat may be advised.
• Coccidia: usually sulfadimethoxine, ponazuril or similar medicines, for several days.
• Supportive care: fluids if dehydrated, and a gentle diet. See gastrointestinal cat diets.

Complete the course. Retest after treatment, since cysts may persist.

Home hygiene

Reinfection is the main problem.

• Scoop litter at least daily, and wash boxes with hot water and disinfectant, then dry. Steam cleaning or boiling water is helpful.
• Wash bedding in hot water.
• Clean floors with a disinfectant such as diluted bleach or quaternary ammonium products, avoiding unsafe products for cats. See cat safe cleaning products.
• Remove feces quickly from outdoor spaces.
• Wash bowls daily. See how to clean cat food bowls.
• Keep kittens separate from other pets until treated.
• Limit carpet and fabric for the infected kitten.

Protecting people

Giardia can occasionally infect humans, causing stomach upset. Coccidia in cats generally does not infect people. Wash hands after handling kittens or litter. Keep children from contact with feces. People with weakened immune systems should take extra care. See toxoplasmosis and cats for related litter hygiene.

Why these parasites keep returning

• Reinfection from the environment.
• Treating only the kitten, not the mother or other pets.
• Stopping medicine early.
• Stress, which weakens immunity.
• Poor sanitation.

Prevention

• Keep a clean litter routine.
• Avoid contaminated water.
• Test new kittens.
• Keep kittens' stress low, and nutrition good.
• Treat all affected pets.

Compare with worms

Roundworms and hookworms are treated with dewormers, but protozoa need other drugs. See kitten deworming guide and worms in cats.

Warning signs

Go to a vet urgently if your kitten has bloody diarrhea, vomiting, lethargy, refuses food or seems dehydrated. See cat dehydration signs and treatment.

What treatment looks like in practice

Expect a few days to a couple of weeks of medication, with careful cleaning every day. You may be asked to bathe the kitten, since cysts cling to fur around the rear and are re-swallowed during grooming. Keep towels separate, and wash them hot. Most kittens improve within days, but retesting is needed to be sure.

Multi-kitten households

If one kitten tests positive, treat all kittens and cats that share space, as your vet advises, even those without signs. Clean everything at the same time, since a half-cleaned environment brings the problem back. Isolating affected kittens helps while treatment takes effect.

Nutrition and recovery

Offer a highly digestible kitten diet, small meals and plenty of fresh water. Kittens recovering from protozoa often need extra calories, so monitor weight weekly. If weight falls or diarrhea returns, tell your vet at once.

Questions owners ask

Can my kitten still go to boarding or grooming? Not until treatment is complete and cleared, since these parasites spread through shared spaces. Do adult cats need testing? If they live with the kitten, ask your vet. How long do cysts survive outdoors? Giardia cysts persist in cool, damp places for weeks, so avoid contaminated water and stagnant puddles. Can I use probiotics? Some vets recommend them, but ask first.

When to see a vet

Take a stool sample to your vet whenever diarrhea lasts longer than a day. Use the US vet directory to find a clinic.